The present invention relates to air cycle houses with a highly airtight and heat-insulating structure which applies either the natural ventilation system dependent on natural convection or the heat-exchange ventilation system using a heat exchanger, as selected according to the weather, and a house ventilation system for such houses.
As an energy-saving measure for so-called new-generation houses intended to provide a more comfortable indoor environment and reduce energy consumption, there are demands for improving air-tightness and heat-insulating property of a house and also achieving planned ventilation through a definite air entrance and exit.
Known ventilation methods for a house with a highly airtight and heat-insulating structure include the natural ventilation system and the heat-exchange ventilation system. The former allows fresh air to enter the house, to circulate therein and to exit out of the house by natural air convection. The latter intends to minimize the indoor heat loss by performing ventilation together with forced heat exchange between the incoming outdoor air and the outgoing indoor air.
The inventor of the present invention has diligently investigated the use of the natural ventilation system, as recently disclosed in Japanese Patent Application Laid-open No. 2000-144957. This technology proposes an air cycle house 8 for practical use, as shown in FIG. 7 of the present application. The air cycle house 8 comprises an exterior wall 81, an interior wall 82 and a wall ventilation layer 83 defined in-between. The wall ventilation layer 83 establishes communication between outdoor air and an underroof space (attic) 84 for ventilation of the inner side of the exterior wall 81. Besides, the entire indoor space enjoys an enhanced heat insulation property from the outdoor air by disposing a wall insulating layer 87 between the interior wall 82 and the wall ventilation layer 83, an underfloor insulating layer 88 below a downstairs floor panel 85 and a ceiling insulating layer 89 above an upstairs ceiling 86. Further, an intermediate ventilation layer 90 allows communication between the downstairs indoor space and the upstairs indoor space. There is also provided an air intake 91 for introducing outdoor air into the downstairs indoor space. In this structure, the introduced air flows out from the downstairs indoor space through a downstairs ceiling 92, passes the intermediate ventilation layer 90 and the upstairs indoor space and reaches the underroof space 84. Thus, warm indoor air naturally rises from the downstairs towards the underroof space 84. In summer, rise of the indoor temperature is suppressed by actively releasing hot air in the underroof space 84 out of the house by a ventilation fan 93. In winter, indoor heat loss is prevented by returning warm air in the underroof space 84 to the downstairs indoor space by a reflux fan 94.
A house relying on the heat-exchange ventilation system is disclosed, for example, in Japanese Patent Application Laid-open Nos. H10-30283 (1998-30283) and H10-245903 (1998-245903). The house comprises a ventilation layer provided around the indoor space and a heat-insulating layer surrounding the ventilation layer externally, wherein a heat exchange ventilator disposed in the ventilation layer enforces heat exchange between outdoor air to be supplied into the house and indoor air to be discharged therefrom.
As far as these conventional technologies are concerned, the natural ventilation system is capable of ensuring a sufficient amount of ventilation rather easily. However, when the inside of the house is air-conditioned, a greater amount of heat is lost in proportion to the ventilation amount. Thus, in regions of intense summer heat or severe winter cold, it is difficult to carry out satisfactory ventilation on a constant basis. An attempt to secure a sufficient amount of ventilation inevitably results in increase of energy load for air conditioning.
On the other hand, the heat-exchange ventilation system is capable of decreasing heat loss inside an air-conditioned house owing to heat exchange between the outdoor air to be taken in (incoming air) and the indoor air to be vented out (outgoing air) However, it cannot provide a sufficient amount of ventilation without a considerably large ventilator. Lack of ventilation not only causes pollution of indoor air and deterioration of interior comfort, but also sacrifices the durability of the house due to incidence of dew condensation, growth of mold and ticks, etc.
In order to improve the interior comfort and the durability of a house, it is desirable to ventilate the house as constantly as possible, throughout a day and a year. From a security point of view, however, it is not recommended to leave windows, etc. open during daily or long-term absence. In terms of energy cost, continuous operation of a ventilator costs too much. In addition, some people, particularly aged persons, find it annoying to conduct appropriate ventilation (e.g. to open and close windows, to change over the ventilator operation) in accordance with the season or the weather.